Image forming apparatus

ABSTRACT

In an image forming apparatus, a carriage mounts a recording head for discharging droplets, and moves in a main scan direction. A guide member slidably guides the carriage. An encoder scale is arranged along the main scan direction. An encoder sensor reads the encoder scale. The carriage includes a head mounting part for mounting the recording head, and a sensor attaching part for attaching the encoder sensor. The sensor attaching part is provided so as to be extended from the head mounting part. The encoder scale is arranged at a location which the encoder sensor can read. A partition member is provided to separate the head mounting part from the sensor attaching part in the carriage. The head mounting part is arranged in a first space, and the sensor attaching part and the encoder scale are arranged in a second space separated from the first apace by the partition member.

TECHNICAL FIELD

The present invention generally relates to an image forming apparatus,and more particularly to the image forming apparatus which includes acarriage mounting a recording head for ejecting droplets.

BACKGROUND ART

As an image forming apparatus such as a printer, a facsimile, a copier,a plotter, a multifunctional apparatus integrating them, or the like,for example, an inkjet recording apparatus is well known as a liquiddischarge recording scheme by using a recording head which is formed bya liquid discharge head (droplet discharge head) for discharging inkdroplets. In the image forming apparatus of the liquid dischargerecording scheme, an image is formed by discharging ink droplets from arecording head onto a sheet being conveyed. The sheet is not limited toa paper sheet. The sheet may be an OHP (Over Head Projector) and othertypes of sheets onto which the ink droplet or other liquid can beadhered, and may be called as a medium to be recorded, a recordingpaper, a recording sheet, or the like. Recording, printing, and the likeare synonymous with forming an image. There are as plurality of serialtype image forming apparatus for forming an image by dischargingdroplets while the recording hoad moves in a main scan direction, and aline type image forming apparatus using a line type head for forming animage by discharging droplets in a state in which the recording headdoes not move.

In order to detect a main scan location of a carriage mounting therecording head, the serial type image forming apparatus includes alinear encoder formed by an encoder scale arranged in the main scandirection and an encoder sensor mounued at a carriage side. However,since the image is formed by discharging droplets from the recordinghead, when mist is adhered to the encoder scale, misreading of a headlocation occurs and detection accuracy of a carriage location isdegraded. Thus, image quality is degraded.

Accordingly, Japanese Laid-open Patent Application No. 2003-081691discloses that the linear encoder is formed by the encoder scalearranged in a vicinity of a carriage conveyance belt and an encodersensor provided at a lateral surface of the carriage, and a shieldingplate is arranged between an upper portion of the carriage conveyance beit at least and the encoder scale.

Moreover, Japanese Laid-open Patent Application No. 2001-113772discloses that the linear encoder is formed by the encoder scalearranged in the vicinity of the carriage conveyance belt and the encodersensor provided at the lateral surface of the carriage. A cover isprovided to cover the encoder sensor and a part of the encoder scale inthe vicinity of the encoder sensor. The cover includes a guide part torguiding the encoder scale to a predetermined location with respect tothe encoder sensor.

However, in the above described technologies, since the recording headof the carriage and the encoder scale are arranged within the samespace, the mist, which is discharged with the droplets from therecording head, goes around the shielding plate and reaches and adheresto the encoder scale or to a portion which is not shielded by the cover.

DISCLOSURE OF THE INVENTION

The present invention solves or reduces one or more OF the aboveproblems.

In an aspect of this disclosure, there is provided an image formingapparatus, including a carriage configured to mount a recording head fordischarging droplets and to move in a main scan direction; a guidemember configured to slidabiy guide the carriage; an encoder scaleconfigured to be arranged along the main scan direction; and an encodersensor configured to be mounted to the carriage and to read the encoderscale, wherein the carriage includes a head mounting part configured tomount the recording head; and a sensor attaching part configured toattach the encoder sensor at least, wherein the sensor attaching part isprovided so as to be extended from the head mounting part; the encoderscale is arranged at a location possible for the encoder sensor attachedto the sensor attaching part to read; a partition member is provided toseparate the head mounting part from the sensor attaching part in thecarriage; and the head mounting part is arranged in a first space, andthe sensor attaching part and the encoder scale are arranged in a secondspace which is separated from the first space by the partition member.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features, and advantages of the present invention willbecome more apparent from the following detailed description when readin conjunction with the accompanying drawings, in which:

FIG. 1 illustrates a perspective view for explaining an outer appearanceof the image forming apparatus.

FIG. 2 illustrates a plan view for explaining a mechanical portion ofthe image forming apparatus.

FIG. 3 is a schematic view for explaining a substantial portion of acarriage part in a first embodiment.

FIG. 4 is a lateral view of the carriage part in the first embodiment.

FIG. 5 is a diagram schematically illustrating a spatial configurationin FIG. 4 according to the first embodiment.

FIG. 6 is a lateral view of the carriage part in a second embodiment.

FIG. 7 is a diagram schematically illustrating a spatial configurationin FIG. 6 according to the second embodiment.

FIG. 8 is a lateral view of the carriage part in a third embodiment.

FIG. 9 is a lateral view of the carriage part in a fourth embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

In the following, embodiments of the present invention will be describedwith reference to the accompanying drawings. An example of an imageforming apparatus 1000 will be briefly described with reference to FIG.1 and FIG. 2. FIG. 1 illustrates a perspective view for explaining anouter appearance of the image forming apparatus 1000. FIG. 2 illustratesa plan view for explaining a mechanical portion of the image formingapparatus 1000.

In the embodiments described below, the “image forming apparatus” 1000being a liquid discharge recording scheme is regarded as an apparatusfor forming an image by discharging liquid onto a medium such as paper,string, fabric, cloth, leather, metal, plastic, glass, wood, ceramics,or the like. Also, an “image formation” may include not only applying animage having a message such as a letter, a graphic, or the like onto themedium but also applying an image such as a pattern which does not havea message (simply, a droplet is landed onto the medium). An “ink” is notlimited to material called ink, and may be genetically denoted as anyliquid used for the image formation such as recording liquid, fixingprocess liquid, simply called liquid, and the like. For example, a DNAspecimen, a resist, a pattern material, resin, or the like may beregarded as the ink. Also, the “image” is not limited to a planar imageand may be an image applied onto a three-dimensionally formed object, animage formed by three-dimensionally modeling a solid object, and thelike.

The image forming apparatus 1000 is regarded as a serial type imageforming apparatus. At an upper lateral side of a body 100, a cover 101is provided to be opened and closed. The mechanical portion inside theimage forming apparatus 1000 may be accessed by opening the cover 101.

As illustrated in FIG. 2, in the mechanical portion, a carriage 4 isslidably retained, in a main scan direction by a guide member 3 (FIG. 3)bridging laterally between main lateral plates 1A and 1B at right andleft sides. The carriage 4 is moved in the main scan direction by atiming belt 8 which is stretched between a driving pulley 6 and a drivenpulley 7 by a main scan motor 5.

The carriage 4 includes multiple recording head units 11 each whichincludes a liquid discharge head regarded as an image forming part fordischarging droplets respective to yellow (Y), cyan (C), magenta (M),and black (B), and a head tank for supplying ink to the liquid dischargehead. In each of the recording head units 11, a nozzle line havingmultiple nozzles is arranged in a sub scan direction perpendicular tothe main scan direction. Each of the recording head units 11 is mountedso that a droplet discharge direction is oriented downward. The multiplerecording head units 11 are retained by a head holder (not shown) as oneunit and mounted to the carriage 4. In the following, the recording headunits 11 may be simply called “recording heads 11”.

Also, an encoder scale 15 is arranged along the main scan direction ofthe carriage 4. An encoder sensor 16 is attached at a side of thecarriage 4. The encoder sensor 16 is formed by a transmissivephotosensor for reading a scale (location identification part) of theencoder scale 15. A linear encoder is formed as a location detectiondevice by the encoder scale 15 and the encoder sensor 16.

On the other hand, under the carriage 4, a conveyance belt 21 isarranged as a conveyance part for conveying a sheet (not shown) in thesub scan direction. The conveyance belt 21 is regarded as an endlessbelt hung on a conveyance roller 22 and tensioning roller 23. Byrotating and driving the conveyance roller 22 through a timing belt 32and a timing pulley 33 by a sub scan motor. 31, the conveyance belt 21is rotated and moved in the sub scan direction.

Furthermore, a maintenance recovery mechanism 49 is arranged at one aideof the main scan direction of the carriage 4 and a lateral side of theconveyance belt 21, to perform a maintenance recovery for the recordingheads 11. The maintenance recovery mechanism 49 may include a cap memberfor capping a nozzle surface (a surface on which nozzles are formed) ofthe recording heads 11, a wiper member for wiping the nozzle surface, anidle discharge receiver for discharging a droplet which does notcontribute to the image formation.

Also, as illustrated in FIG. 1, a paper feed and ejection tray 103 isdetachably mounted to the body 100. The paper feed and ejection tray 103includes a paper feed part for feeding a sheet to the conveyance belt21, and a paper ejection part for ejecting the sheet on which the liquiddischarged from the recording heads 11 as an image formation part isadhered and an image is formed.

In the image forming apparatus 1000 formed as described above, the sheetfed by the paper feed part is intermittently conveyed by the conveyancebelt 21, and the recording heads 11 are driven in response to an imagesignal by moving the carriage 4 in the main scan direction, thereby oneline is recorded by discharging droplets onto the stopped sheet. After apredetermined amount of nhe sheet is conveyed, the image is formed ontothe sheet by repeating an operation for performing recording of a nextline. When the image is formed, the sheet is ejected.

Next, a first embodiment in the image forming apparatus 1000 will bedescribed with reference to FIG. 3 through FIG. 5. FIG. 3 is a schematicview for explaining a substantial portion of a carriage part in thefirst embodiment. FIG. 4 is a lateral view of the carriage part in thefirst embodiment. FIG. 5 is a diagram schematically illustrating aspatial configuration in FIG. 4 according to the first embodiment.

For the carriage 4, a carriage cover 42 is provided to cover an upperportion of a head mounting part 41 at the upper portion of the headmounting part 41 which mounts the recording heads 11. Also, a sensorattaching part 43 is provided. The sensor attaching part 43 is regardedas a portion which forms a single member with the carriage cover 42 andwhich is extended from the head mounting part 41 along a direction, forfeeding the sheet.

A head side substrate 112 mounting a head side electrical component isattached to a downward surface of the sensor attaching part 43. Anencoder sensor 16 is provided on the head side substrate 112. Theencoder scale 11 is arranged at a location readable for the encodersensor 16.

The guide member 3 for slidably guiding the carriage 4 is formed by asteel plate, and includes guide surfaces 301, 302, and 303 to be asupporting surface in order to slidably guide the carriage 4. The headmounting part 41 of the carriage 4 includes a sliding part 401 whichslidably contacts the guide surface 301 of the guide member 3, a slidingpart 402 which slides in contact with the guide surface 302, and asliding part (slider) 403 which slides in contact with the guide surface303. In this case, the guide surface 301 of the guide member 3 is usedas a surface to determine a location of the carriage 4 in height. Theguide surface 302 is used as a surface (rotation stopper) to receive amoment of force due to a weight of the carriage 4 itself. The guidesurface 303 is used as a surface to determine a location of the carriage4 in the sub scan direction.

The guide member 3 is arranged for the entirety of the main scandirection, and is also used as a partition member for separating thehead mounting part 41 from the sensor attaching part 43 and the encoderscale 15 in the carriage 4.

Also, at the downward surface of the sensor attaching part 43 of thecarriage 4, a front stay 61 contacting the guide member 3 is arranged.

Moreover, a concave portion 50 is provided to the carriage cover 42 ofthe carriage 4 between a side of the head mounting part 41 and thesensor attaching part 43. Then, a partition member 51 is provided to thecover 101. The partition member 51 is fitted in the concave portion 50of the carriage cover 41, and separates the head mounting part 41 fromthe sensor attaching part 43 at an upper portion side of the carriage 4.The partition member 51 is arranged in the entirety of the main scandirection.

By this configuration, the head mounting part 41 is separated from thesensor attaching part 43 even at the upper side of the carriage 4.Therefore, by the partition member 51 fitting in the concave portion 50,it is possible to approximately shield the sensor attaching part 43 fromthe head mounting part 41.

On the other hand, between the carriage 4 and the conveyance belt 21, apressure plate 71 is arranged with respect, to a rear stay 62, and apaper ejection guide 73 under the guide member 3. The pressure plate 71includes, at a tip portion, a pressure roller 72 for pressing the sheetto the conveyance belt 21. The paper ejection guide 73 guides the sheetejected from the conveyance belt 21.

By this configuration, as illustrated in FIG. 5, a space where thecarriage 4 moves is divided into a space 501 where the head mountingpart 41 of the carriage 4 moves, and a space 502 where the sensorattaching part 43 of the carriage 4 moves and the encoder scale 15 isarranged.

In the above cordiguration, in a case in which the droplets aredischarged from the recording heads 11 mounted to the head mounting part41 of the carriage 4, even if mist occurs and floats in the space 501,the mist is shielded by the guide member 3 and the partition member 51.Even if the sensor attaching part 43 moves, the mist hardly enters thespace 502 where the encoder scale 15 is arranged. It is possible toreduce adherence of the mist to the encoder scale 15.

As described above, the carriage 4 includes the head mounting part 41for mounting the recording heads 11 and at least the sensor attachingpart 43 for attaching the encoder sensor 16. The sensor attaching part43 is provided so as to be extended from the head mounting part 41. Theencoder scale 15 is arranged at the location which the encoder sensor 16can read. The partition member 51 is arranged to separate the headmounting part 41 from the sensor attaching part 43 in the carriage 4.Then, the head mounting part 41 of the carriage 4 is arranged in thespace 501, and the sensor attaching part 43 and the encoder scale 15 arearranged in the space 502 different from the space 501 in which thespaces 501 and 502 are separated by the partition member 51. It ispossible to reduce the adherence of the mist to the encoder scale 15.

Next, a second embodiment will be described with reference to FIG. 6 andFIG. 7. FIG. 6 is a lateral view of the carriage part in the secondembodiment. FIG. 7 is a diagram schematically illustrating a spatialconfiguration in FIG. 6 according to the second embodiment. In thesefigures, parts that are the same as those illustrated in the previouslydescribed figures are given by the same reference numbers.

In the second embodiment, the sensor attaching part 43 is providedupward from the head mounting part 41 of the carriage 4. The encoderscale 15, which is read by the encoder sensor 16, is arranged above thehead mounting part 41. The guide member 3 is arranged above the headmounting part 41 and below the encoder sensor 16 of the sensor attachingpart 43. Thus, the sensor attaching part 43 is separated from the headmounting part 41.

Moreover, between the front stay 61 and the sensor attaching part 43,the partition member 51 is provided to fit in the concave portion 50formed on the sensor attaching part 43.

By the above configuration, as illustrated in FIG. 7, a space where thecarriage 4 is divided into an upper space and a lower space by the guidemember 3 and the partition member 51. In a apace 501 a as the upperspace, the head mounting part 41 of the carriage 4 moves. In a space 502a different from the space 501 a, the sensor attaching part 43 of thecarriage 4 moves and the encoder scale 15 is arranged.

Accordingly, similar to the first embodiment, in a case in which thedroplets are discharged from the recording heads 11 mounted to the headmounting part 41 of the carriage 4, even if mist occurs and floats inthe space 501 a, the mist is shielded by the guide member 3 and thepartition member 51. Even if the sensor attaching part 43 moves, themist hardly enters the space 502 a where the encoder scale 15 isarranged. It is possible to reduce adherence of the mist to the encoderscale 15. Moreover, the encoder scale 15 is arranged in the space 502 asectioned above the head mounting part 41. Since the mist does not floatupward easily because of gravity, it is possible to acquire a furtherreduction effect of mist adherence.

Next, a third embodiment will be described with reference to FIG. 8.FIG. 8 is a lateral view of the carriage part in the third embodiment.In FIG. 8, parts that are the same as those illustrated in thepreviously described figures are given by the same reference numbers.

In the third embodiment, instead of the partition member 51 in the firstembodiment, a mist collection member 81 is provided as a partitionmember. The mist collection member 81 may be formed by a brush, afilter, a porous member, a charge member, or the like.

By this configuration in the third embodiment, it is possible to acquirea further mist reduction effect of mist adherence.

Next, a fourth embodiment will be described with reference to FIG. 9.FIG. 9 is a lateral view of the carriage part in the fourth embodiment.In FIG. 9, parts that are the same as those illustrated in thepreviously described figures are given by the same reference numbers.

In the fourth embodiment, instead of the partition member 51 in thesecond embodiment, the mist collection member 81 is provided as thepartition member. The mist collection member 81 may be formed by thebrush, the filter, the porous member, the charging member, or the like.

By this configuration in the fourth embodiment, it is possible toacquire a further mist redaction effect of mist adherence.

Furthermore, for example, in the first embodiment, the encoder sensor 16and the encoder scale 15 may be arranged at an upper surface side of thesensor attaching part 43. Similarly, in the second embodiment, theencoder sensor 16 and the encoder scale 15 may be arranged at a side ofthe sensor attaching part 43 which is opposite to the head mounting part41.

In the above described embodiments, applications for the image formingapparatus 1000 having a printer configuration are described. However,the first through fourth embodiments are not limited to the printerconfiguration, and may be applied to another image forming apparatussuch as a multifunction apparatus including a printer, a facsimile, acopier, and the like. Also, the first through fourth embodiments may beapplied to an image forming apparatus using liquid or fixing processliquid other than the ink in the narrow sense, patterning material, orthe like.

The present invention is not limited to the specifically disclosedembodiments, and variations and modifications may be made withoutdeparting from the scope of the invention.

The present application is based on Japanese Priority Application No.2010-277462 filed on Dec. 13, 2010, the entire contents of which arehereby incorporated by reference.

1. An image forming apparatus, comprising: a carriage that mounts arecording head for discharging droplets and to move in a main scandirection; a guide member that slidably guides the carriage; an encoderscale that is arranged along the main scan direction; and an encodersensor that is mounted to the carriage and to read the encoder scale,wherein the carriage includes a head mounting part that mounts therecording head; and a sensor attaching part that attaches the encodersensor at least, wherein the sensor attaching part is provided so as tobe extended from the head mounting part; the encoder scale is arrangedat a location possible for the encoder sensor attached to the sensorattaching part to read; a partition member is provided, in which thepartition member projects from a stay toward between the head mountingpart, of the carriage and the encoder sensor in a horizontal direction,the stay being arranged facing an outer surface of the carriage from asub scan direction; and the head mounting part is arranged in a lowerspace of the partition member, and the encoder sensor and the encoderscale are arranged in an upper space of the partition member.
 2. Theimage forming apparatus as claimed in claim 1, wherein at least aportion of the partition member is overlapped with a portion of thecarriage in a verticl direction the guide member is used as thepartition member.
 3. The image forming apparatus as claimed in claim 1,wherein at least a portion of the partition member is accommodated in aconcave portion provided between the head mounting part of the carriageand the encoder sensor.
 4. The image forming apparatus as claimed inclaim 1, wherein the sensor attaching part extends upward from the headmounting part in a height direction.
 5. The image forming apparatus asclaimed in claim 1, wherein a mist collection member for collecting mistis provided between a space where the head mounting part of the carriageis arranged and another space where the sensor attaching member isarranged.
 6. The image forming apparatus as claimed in claim 1, whereinthe partition member is arranged for an entirety of the main scandirection.